While Facebook's overall user growth has naturally slowed down a bit - monthly active users grew 3% on a quarter-to-quarter basis and 14% year-over-year - the number of users who access Facebook via mobile devices is still growing rapidly. Of Facebook's 1.07 billion mobile users, 399 million access Facebook exclusively on mobile devices, representing an increase of more than 80% over last year's second quarter and of almost 20% compared to the March quarter of this year. Thankfully, Facebook has successfully figured out how to monetize its mobile users, because one thing is now more clear than ever: Facebook's future is mobile.This charts shows Facebook's monthly active users, broken down by the type of device they access the social network on.